Endoscopy Brief: Identifying the cause of acute cough and respiratory distress in a toy poodle

A 13-year-old 12-lb (5.5-kg) intact male toy poodle was presented to Mississippi State University's College of Veterinary Medicine for evaluation of coughing and increased respiratory effort and exercise intolerance of four days' duration. The dog's vaccinations, heartworm preventive administration, and negative heartworm test results were current.

Figure 1. A right lateral thoracic radiograph at presentation. Mild generalized cardiomegaly is causing dorsal displacement of the tracheal bifurcation (arrow). Increased soft tissue opacity can be seen cranial to the cardiac silhouette (arrowhead).

At initial presentation, the dog was bright and alert. Its hydration status and temperature were normal; its heart rate (160 beats/min) and respiratory rate (54 breaths/min) were elevated. A grade I/VI systolic heart murmur was auscultated, with the point of maximum intensity over the mitral valve area. Pulmonary auscultation revealed bilateral crackles cranioventrally. A cough could be frequently elicited with tracheal palpation. The patient's respiratory distress worsened during the physical examination, and the patient was placed in an oxygen cage at 40% oxygen after initiation of intravenous fluids administered at a maintenance rate. Pulse oximetry revealed an SpO2 of 90%.

Figure 2. A ventrodorsal thoracic radiograph at presentation. There is an intense, focal alveolar pattern in the left cranial lung lobe (arrows), which contains a prominent air bronchogram (arrowhead). Mild generalized cardiomegaly is present.

A complete blood count revealed leukocytosis (total WBC count = 21,180/μl; reference range = 6,000 to 17,000/μl) with neutrophilia (15,190/μl segmented neutrophils; reference range = 3,000 to 11,500/μl) and a left shift (1,302/μl band neutrophils; reference range = 0 to 300/μl). A serum chemistry profile revealed no significant abnormalities. Thoracic radiographs revealed mild generalized cardiomegaly (Figures 1 & 2). Radiographic evidence of heart failure was not seen, and the heart enlargement was not considered severe enough to compress the mainstem bronchi and contribute to the cough. Inspiratory and expiratory lateral views revealed no evidence of tracheal collapse. On the right lateral thoracic radiograph, an area of increased soft tissue opacity was seen cranial to the heart. On the ventrodorsal view, this radiopacity was in the region of the left cranial lung lobe. Closer evaluation revealed both interstitial and alveolar lung patterns in this region. A single air bronchogram appeared to be traversing the long axis of the left cranial lung lobe. Radiographic findings were compatible with consolidation of the left cranial lung lobe.

Figure 3. The tracheal bifurcation during expiration. The partially collapsed left mainstem bronchus is on the right side of the image.

The differential diagnoses for these findings include lobar pneumonia, pulmonary neoplasia, and, much less likely, lung lobe torsion. Bronchoscopy and a bronchoalveolar lavage were performed to further assess the lung abnormalities.

BRONCHOSCOPIC EXAMINATION AND INITIAL THERAPY

Figure 4. The left cranial lobar and caudal segmental bronchi of the left cranial lung lobe during inspiration. The bronchi are moderately erythematous.

After partial patient stabilization (respiratory rate = 20 breaths/min and spo2 = 97% with concurrent oxygen therapy), the patient was anesthetized and positioned in sternal recumbency. A 5-mm-diameter video bronchoscope (Olympus BF Type P20D—Olympus) was used to examine the oral cavity, pharynx, and trachea. No abnormalities were found. The bronchoscope was then advanced to the tracheal bifurcation.